The present invention relates to pulp refining equipment, and more particularly to a sealing ring construction for use in pulp refiner units which utilize counter-rotating discs. The present invention is directed to a novel pair of rings which are mounted on the pulp refiner unit, internally thereof, to substantially ensure flow of material to the grinding interface between the discs.
Pulp refiner units of the "double disc" type are machines which include a pair of counter-rotating discs mounted within a housing for receiving raw material, such as fibrous wood particles or solids to grind the solids into fibers or "pulp" for use in manufacturing paper, paperboard and engineered wood products such as particleboard, waferboard, etc. The housing includes an opening in front of which is mounted a stock feed inlet for channeling the raw material toward a first or feed disc which includes a plurality of passageways for directing the material to the interface between the discs. However, a problem resides in providing an efficient seal between the passageways provided in the feed disc and the opening in the casing. Stated differently, it is undesirable to have raw material be drawn from the stock feed inlet through the opening to bypass the passageways in the feed disc so as to be misdirected into the space between the discs and the housing. If that occurs, the raw material will not be pulped. Various proposals have been made for providing some type of sealing ring construction on disc refiners.
An example is the construction set forth in Horstman, U.S. Pat. No. 3,273,809. In that patent, a sealing ring construction is disclosed in which a first seal ring is mounted on the housing or casing so as to concentrically receive therewithin an inlet ring which is mounted on the feed disc. The inlet ring extends radially inwardly of the opening and therefore receives material directly against its external vertical face during rotation of the feed disc. Moreover, the gap or annular region presented between the outside surface of the inlet ring and the inside surface of the seal ring is open to the stock inlet, thereby presenting a direct route whereby raw material may be transferred into the space between the housing and the discs, thereby bypassing the passageways in the feed disc. While it is possible to adjust the gap between the seal and inlet rings, obviously some clearance must be provided for operation inasmuch as the rings are relatively movable. In addition, there must be provided some gap between the face of the inlet ring and the adjacent surface of the stock feed inlet so that contact does not occur. This all means that there is a means by which raw material may be directed to bypass flow to the passageways in the feed disc.
Moreover, another disadvantage results from the construction shown in Horstman, inasmuch as raw material drawn into the annular region between the seal and inlet rings sweeps over the upper shoulder of the chute of the stock feed inlet, which deleteriously abrades that surface. As mentioned previously, action of the raw material being drawn into the passageways of the feed disc will also tend to wear down the surface of the inlet ring, all of which means that the useful life of the inlet ring and stock feed inlet is short and expensive.
Other proposals have been made to provide sealing ring constructions for disc refiners units, one of which is Horstman, et al., U.S. Pat. No. 3,843,065. There, a sealing ring construction is modified so that a labyrinth passage is provided in which fluid under pressure creates what is referred to as a "dynamic dam" to block and prevent unrefined raw material from being directed between the seal and inlet rings. However, in order to provide such a construction, specially formed seal and inlet rings must be formed, and it is still problematical to replace the rings when they become worn.
Because of the attendant disadvantages in the prior art with respect to sealing ring constructions for pulp refiner units, it is a general object of the present invention to provide a sealing ring assembly which includes a seal ring defined by a circular flange section from which extends a projective ring section. The flange section is detachably mounted on the stock feed inlet within the housing and the projecting ring extends toward the discs. An inlet ring is defined by a flange section from which extends a projecting ring section. The flange section is detachably mounted on the disc closest to the stock feed inlet, and the projecting ring extends from the flange section toward the housing opening for concentrically receiving the seal ring's projective ring section. This construction results in an annular clearance region defined between the projecting ring sections which is in a reverse direction from the flow path of raw material being drawn into the passageways of the feed disc.
It is another object of the present invention to provide a sealing ring assembly, as defined above, in which the annular clearance region is conical in form. That construction permits ready clearance adjustment between the seal and inlet rings, merely by providing a single adjustment, as opposed to at least two adjustments on prior art sealing ring constructions. That feature of the present invention will be more fully described at a later point herein.
Still another object of the present invention is to provide a sealing ring assembly, as defined above, in which the seal ring, and a particular portion of its flange section, is dimensioned to extend below the opening in the stock feed inlet. Inasmuch as the inlet ring is concentrically mounted to surround the projecting ring section of the seal ring, material does not directly engage the inlet ring, which rotates with the feed disc, thereby resulting in a significant diminution in wear on the inlet ring. Because the seal ring is stationary, it may receive impact of the raw material, as it is being drawn through the stock feed inlet into the passageways of the feed disc, without the degree of abrading wear which would result on a rotating ring.
Yet a further object of the present invention is to provide a sealing ring assembly, as described above, in which the projecting ring section of the seal ring has a inwardly tapered, conical outer surface and the projecting ring section of the inlet ring has an outwardly tapering conical inner surface. By so constructing the opposed outer and inner surfaces of the seal and inlet rings, respectively, trouble-free operation is ensured, and adjusting the gap of the annular clearance region between the projecting ring sections is readily made.
These and additional objects and advantages of the present invention will be more readily understood after a consideration of the drawings and the following detailed description of the preferred embodiment.